A: Hello, thanks for reaching out to us! Our size measurements are the best way to find out which size will be best for you. I would recommend choosing one of your favorite shirts, laying it flat, and then measuring the length (from shoulder to hem) and width (about one inch below the bottom of the sleeve) of the tee. I would then compare those measurements to the measurements provided to help you decide which size will work best for you. Here are the measurements for our boys' tees: XS has a width of 16" and a length of 21". Small has a width of 17" and a length of 22.5". Medium has a width of 18" and a length of 24". Large has a width of 19" and a length of 25.5". XL has a width of 20" and a length of 27". I hope that helps! Please let me know if you have any questions or need anything else. Have a great day!